Arrangement for a band saw apparatus



July 22, 1969 H. AKRENIUS ARRANGEMENT FOR A BAND SAW APPARATUS 2 Sheets-Sheet 1 Filed Feb. 14, 1967 Juiy 22, 1969 H. AKRENIUS 3,456,695

ARRANGEMENT FOR A BAND SAW APPARATUS Filed Feb. 14, 1967 2 Sheets-Sheet 2 3,456,695 ARRANGEMENT FOR A BAND SAW APPARATUS Huvi Israel Akrenins, Uunisepantie 5, Helsinki, Finland Filed Feb. 14, 1967, Ser. No. 616,077 Claims priority, application Finland, Oct. 28, 1966, 2,861/66 Int. Cl. B2711 13/00 US. Cl. 14317 9 Claims ABSTRACT OF THE DISCLOSURE A safety arrangement for a band saw having two blade wheels and a band blade running over the wheels and wherein an operating lever is displaceable between start and stop positions for a drive means for the blade wheels. The operating lever is utilized to apply brake means to the blade wheels when the drive means is stopped, whereas an openable access door of a cover frame is locked when the lever is placed in the start position. Additionally, the drive means is deenergized when the cover is opened.

BRIEF SUMMARY OF THE INVENTION The present invention relates to an arrangement for a band saw comprising at least two, and possibly more, blade Wheels, which are placed one above the other and rotate on parallel axles, a band blade running over the blade wheels, an electric motor for the blade Wheels and a cover frame, which essentially encloses the band blade and the blade wheels.

Band saws of this type are very often used in industrial joinery to saw wood or the like and in the provision industry to cut meat and bones. In a band saw, the blade moves with considerable speed and after the electric motor driving the blade wheels has been stopped, the blade continues to rotate, even for several minutes, due to the inertia of the blade wheels, thus constituting a continuous danger to the person operating the machine.

In order to improve safety conditions, it has been known to provide at least one of the blade wheels of the band saw with a brake, by means of which the blade wheel is stopped by pressing a pedal connected with the brake after the electric motor has been stopped. In a band saw such as this, there is always the danger that the operator will forget to press the brake pedal and the blade continues to rotate for a period as has been described above.

An object of this invention is to eliminate the above disadvantage and to improve working safety in connection with band saws. The invention is mainly characterized in that the operating lever of the electric motor is connected to a brake acting upon the axle of one of the blade wheels, the brake being automatically placed in the braking position when the motor is stopped by the operating lever, the operating lever being provided with means for locking the cover of the frame when the motor is started by the operating lever and the cover of the frame being provided with means for preventing the starting of the electric motor when the cover is open.

Due to the fact that the operating lever is connected to the brake, the blade of the band saw is stopped simply by turning the operating lever to the stopping position, which must be done in order to stop the saw. Thus no pressing of a pedal or any other measure is required to stop the blade, but the brake is applied automatically depending on the position of the operating lever and cannot be neglected. Since the cover of the frame is prevented from opening as long as the saw is running and the saw cannot be started as long as the cover is open there is no risk of contact with the mobile parts of the saw before the blade has stopped rotating and there is 3,456,595 Patented July 22, 1969 no risk that the saw is started by mistake when the movable parts are repaired or cleaned.

BRIEF DESCRIPTION OF THE DRAWING DETAIL DESCRIPTION OF THE INVENTION The band saw according to the invention comprises a box-like frame 1, having a side Wall with an openable cover 2 mounted on hinges 3. In the upper part of the frame a horizontal axle is mounted, which supports a blade wheel 4, and in the lower part of the frame a horizontal axle 6 is mounted, which supports a blade wheel 7. The axle 6 is driven by means of an electric motor 8. A band blade 5 runs around both blade wheels.

At the forward part of the frame 1 there is mounted an axle 9, which extends parallel with the aforesaid axles and one end of which is rigidly joined to an operating lever 10, the opposite end being provided with, a cross handle 11. A cogged plate lock 12 is fastened to the part of the axle 9 which is inside of the frame (FIGS. 3 and 4), and operates a microswitch 13 which is attached to the frame, and joined to the starting circuit of the electric motor 8 by the wires 14, 15. The lock plate and microswitch are fitted in relation to each other so that when the operating lever is in the stop position A, as shown in FIGURE 3, the microswitch opens the circuit connected to wires 14 and 15 and when the operatitng lever is in the starting position B, as shown in FIGURE 4, the microswitch closes the circuit connected to wires 14 and 15.

The cross handle 11 is hingedly connected to a rod 16, which is mounted at 16' to the frame so that it can slide linearly back and forth in the frame when the operating handle is turned. The rod is fitted so that it can engage a brake 17 arranged on the axle 6 of the blade Wheel 7. The brake comprises two brake shoes 18, 19, which are hingedly connected to each other and fastened to the frame, and a spring arrangement 21 acts on shoes 18, 19, to urge the brake shoes against the axle 6. The operating lever, rod and brake are so arranged that when the operating lever is in the stop position A (FIG. 3) the rod is pulled back from between the brake shoes, whereby the spring arrangement 21 presses the brake shoes against the axle 6 to brake the same, but when the operating lever is turned to the starting position, the rod 16 is thrust forward between two rolls 22, 23 mounted on the brake shoes, to move the same apart and out of contact with the axle 6.

The operating lever is additionally provided with a projection 24, which acts together with a catch 25 on the cover 2 so that when the operating lever is in the stop position A, the projection 24 is removed from the catch 25, but when the operating lever is in the starting position B, the projection 24 has moved in front of the catch 25 preventing the opening of the cover as may be seen in FIGURE 4.

A tenon 26 is fixed to the side of the cover catch 25 facing the frame, and in the corresponding region in the frame there is a spring-loaded rod 27 mounted in bearings, which activates a microswitch 28, which is connected to the starting circuit of the electric motor by the Wires 29, 30. The arrangement of the tenon 26, the rod 27 and the microswitch 28 is such that when the cover is closed, the tenon 26 presses the rod 27 inwards, and thus the rod 27 presses against the microswitch 28 closing the circuit connected to the wires 29 and 30 whereas when the cover is open the rod 27 is pressed outward by the spring of the microswitch 28 whereby the circuit connected to the wires 29 and 30 is opened.

It can be seen from the above that in order to start the electric motor both microswitches 13 and 28 must be closed at the same time. When the cover is open, the motor will not start if the operating lever is turned to starting position B, because the microswitch 28 will still be open.

When the cover is closed and the operating lever is turned from the stop position A to the starting position B, the electric motor is started at the same time that the rod 16 release the brake 17 and the projection 24 on the operating lever prevents the opening of the cover. When the oper ating lever is turned the other way, the motor stops at the same time that the rod allows the brake to be activated and the cover is unlocked.

The locking of the cover has been described to take place simply by means of the fixed projection 24 on the operating lever. In some cases it may be preferable to place the locking point and the operating lever further apart, in which case it may be advantageous to connect the operating lever with a suitable rod arrangement, which engages the cover and locks it when the operating lever i turned to the starting position. Instead of the microswitch 28, it may be possible to use a different arrangement to prevent the starting of the motor as long as the cover remains open, for instance by a tenon mounted in bearings in the frame, which by means of a spring is pushed in front of the operating lever preventing such lever from being turned as long as the cover is open, and which tenon is pushed away from the operating lever by the cover when the cover is closed.

Thus the drawing and the accompanying specification are only intended to illustrate the concept of the invention, and many modifications and variations thereof are possible.

What is claimed is:

1. A band saw comprising two blade wheels, parallel axles supporting said blade wheels for rotation, a band blade running over the blade wheels, drive means for driving the blade wheels, a cover frame substantially enclosing the band blade and the blade wheels, an openable cover on said frame, an operating lever for the drive means, said operating lever being displaceable between start and stop positions for the drive means, a brake means for acting upon the axle of one of the blade wheels, said brake means having operative and inoperative positions, means coupling the operating lever and the brake means such that the brake means is automatically placed in operative position when the operating lever is moved to stop the motor, means on the operating lever tor locking the cover of the frame when the operating lever is moved to start the drive means and means on said cover for preventing the starting of the drive means when the cover is open.

2. A saw as claimed in claim 1 wherein said brake means comprises pivotally connected brake shoes urged against the axle of the said one blade wheel, said means coupling the operating lever and the brake means comprising a rod connected to said operating lever for being moved therewith to engage the brake shoes and pivotably displace the same from the axle of said one blade wheel when the operating handle is turned to the starting position.

3. A saw as claimed in claim 1 wherein said means on the operating lever for locking said cover comprises a projection on said lever which slides in front of the cover of the frame preventing it from being opened when the operating lever is in the starting position.

4. A saw as claimed in claim 1 wherein said drive means is an electric motor.

5. A saw as claimed in claim 4 comprising a microswitch controlling the energization of the electric motor, said means for preventing the starting of the motor when the cover is open comprising an element on said cover which closes the microswitch only when the cover is closed.

6. A saw as claimed in claim 5 comprising a second microswitch also controlling the energization of the electric motor, and means coupled to the operating lever for closing said second microswitch when the lever is moved to the start position.

7. A saw as claimed in claim 3 comprising switch means mounted on the frame for controlling the energization of the drive means, a catch member on said cover, said means on the cover for preventing the starting of the drive means when the cover is open comprising a tenon on said catch member for closing the switch means only when the cover is closed, said means which locks the cover when the lever is in the position to start the drive means comprising a projection on the lever which is positioned adjacent the catch member in said latter position of the lever to prevent opening of the cover.

8- A saw as claimed in claim 2 wherein said rod is supported for slidable movement, said brake shoes including respective rolls between which the rod is inserted when the operating lever is moved to the start position, to pivotably displace the brake shoes.

9. A saw as claimed in claim 8 comprising spring means acting on the brake shoes adjacent the rolls in a direction perpendicular to the direction of sliding of the rod.

References Cited UNITED STATES PATENTS 1,474,447 11/ 1923 Schroeder 192--2 2,311,268 2/1943 Tannewitz 143-17 2,500,321 3/1950 Petersen 143-17 FOREIGN PATENTS 619,117 3/ 1949 Great Britain.

ANDREW R. JUHASZ, Primary Examiner J. F. COAN, Assistant Examiner US. Cl. X.R. 

